The objective of the proposed investigation is to define the role of bacterial pili in the pathogenesis of infections in the urinary tract. The pathogenicity of piliated and non-piliated strains of Proteus mirabilis will be compared in rats. The effect of pili on bacterial interaction with cells of the urinary tract will be examined in vitro. Pili will be purified and used to study the role of humoral antibody, both serum and secretory, on the properties of piliated organisms. The structure of the pili will be investigated and the mechanism of their interaction with the receptor site on the host cell surface will be studied. BIBLIOGRAPHIC REFERENCES: Harrison, W.O., Silverblatt, F.J., Turck, M. Gentamicin Nephrotoxicity: Failure of three cephalosporins to potentiate injury in rats. Antimicrobial Agents and Chemotherapy, 8:209-215, 1975. Silverblatt, F.J. Antibiotic Nephrotoxicity: A review of pathogenesis and prevention. Urol. Clin. N.A., 2:557-567, 1975.